DLARZ(3)       LAPACK routine of NEC Numeric Library Collection       DLARZ(3)



NAME
       DLARZ

SYNOPSIS
       SUBROUTINE DLARZ (SIDE, M, N, L, V, INCV, TAU, C, LDC, WORK)



PURPOSE
            DLARZ applies a real elementary reflector H to a real M-by-N
            matrix C, from either the left or the right. H is represented in the
            form

                  H = I - tau * v * v**T

            where tau is a real scalar and v is a real vector.

            If tau = 0, then H is taken to be the unit matrix.


            H is a product of k elementary reflectors as returned by DTZRZF.




ARGUMENTS
           SIDE      (input)
                     SIDE is CHARACTER*1
                     = 'L': form  H * C
                     = 'R': form  C * H

           M         (input)
                     M is INTEGER
                     The number of rows of the matrix C.

           N         (input)
                     N is INTEGER
                     The number of columns of the matrix C.

           L         (input)
                     L is INTEGER
                     The number of entries of the vector V containing
                     the meaningful part of the Householder vectors.
                     If SIDE = 'L', M >= L >= 0, if SIDE = 'R', N >= L >= 0.

           V         (input)
                     V is DOUBLE PRECISION array, dimension (1+(L-1)*abs(INCV))
                     The vector v in the representation of H as returned by
                     DTZRZF. V is not used if TAU = 0.

           INCV      (input)
                     INCV is INTEGER
                     The increment between elements of v. INCV <> 0.

           TAU       (input)
                     TAU is DOUBLE PRECISION
                     The value tau in the representation of H.

           C         (input/output)
                     C is DOUBLE PRECISION array, dimension (LDC,N)
                     On entry, the M-by-N matrix C.
                     On exit, C is overwritten by the matrix H * C if SIDE = 'L',
                     or C * H if SIDE = 'R'.

           LDC       (input)
                     LDC is INTEGER
                     The leading dimension of the array C. LDC >= max(1,M).

           WORK      (output)
                     WORK is DOUBLE PRECISION array, dimension
                                    (N) if SIDE = 'L'
                                 or (M) if SIDE = 'R'



LAPACK routine                  31 October 2017                       DLARZ(3)